When is it OK for Christians to advocate the killing of whole cities full of people and mass slaughter?

I would say when those people are all posing an immediate threat to the life of other people you would be in the clear. Which is probably a pretty rare event.

Less clear would be if there were some situation in which such a mass killing would somehow save the lives of a larger number of people. I am not sure where Christianity stands on that, actually, but I feel like it is possible that it would be OK.

And he sent you on a mission, saying, 'Go and completely destroy those wicked people, the Amalekites; make war on them until you have wiped them out. 1 Sam 15:18

Fck the bible. I detest it like I detest all things wicked.

Matthew 5:41-48

"41 If anyone forces you to go one mile, go with them two miles. 42 Give to the one who asks you, and do not turn away from the one who wants to borrow from you.43 “You have heard that it was said, ‘Love your neighbor[a] and hate your enemy.’ 44 But I tell you, love your enemies and pray for those who persecute you, 45 that you may be children of your Father in heaven. He causes his sun to rise on the evil and the good, and sends rain on the righteous and the unrighteous. 46 If you love those who love you, what reward will you get? Are not even the tax collectors doing that? 47 And if you greet only your own people, what are you doing more than others? Do not even pagans do that? 48 Be perfect, therefore, as your heavenly Father is perfect."

"41 If anyone forces you to go one mile, go with them two miles. 42 Give to the one who asks you, and do not turn away from the one who wants to borrow from you.43 “You have heard that it was said, ‘Love your neighbor[a] and hate your enemy.’ 44 But I tell you, love your enemies and pray for those who persecute you, 45 that you may be children of your Father in heaven. He causes his sun to rise on the evil and the good, and sends rain on the righteous and the unrighteous. 46 If you love those who love you, what reward will you get? Are not even the tax collectors doing that? 47 And if you greet only your own people, what are you doing more than others? Do not even pagans do that? 48 Be perfect, therefore, as your heavenly Father is perfect."

Mathew 10:

34 Do not suppose that I have come to bring peace to the earth. I did not come to bring peace, but a sword.35 For I have come to turn `a man against his father, a daughter against her mother, a daughter-in-law against her mother-in-law - 36 a man's enemies will be the members of his own household.' 37 Anyone who loves his father or mother more than me is not worthy of me; anyone who loves his son or daughter more than me is not worthy of me;

He sounds like a jealous prick. Not only does he demand that we love Him above all others, even our own children, but He goes farther and condemns them to death? WTF?

God of peace and love my ass. He's a demon and not worthy of ME!

"I'm a tranvestwhite and ask that you please use my preferred racial pronoun, "human." -The Captain

I would say when those people are all posing an immediate threat to the life of other people you would be in the clear. Which is probably a pretty rare event.

Less clear would be if there were some situation in which such a mass killing would somehow save the lives of a larger number of people. I am not sure where Christianity stands on that, actually, but I feel like it is possible that it would be OK.

No need to be posing an immediate threat, any threats can be entirely imagined and Christians can easily justify murder and rape.

After all, just what can you do with someone that is an enemy of your god? Could there be anything more evil to the theist than their god's enemy?

"I'm a tranvestwhite and ask that you please use my preferred racial pronoun, "human." -The Captain